Helen Boussalis

Strain-Based Deformation Shape-Estimation Algorithm for Control and Monitoring Applications

A new deformation shape-sensing methodology is investigated for the purposes of real-time condition assessment, control, and health monitoring of flexible lightweight aerospace structures. The fiber optic strain sensing technology was recently proposed by the NASA Dryden Flight Research Center. The methodology implements the use of fiber optic sensors to obtain strain measurements from the target structure and to estimate the corresponding displacement field. In this paper, the methodology is investigated through an experimental aluminum winglike swept-plate model. The proposed algorithm is implemented for three distinct loading cases and compared to a well-established modal-based shape-estimation algorithm. The estimation results from both methods are also compared to reference displacements from photogrammetry and computational analyses. The estimation error for each method is quantified using the root-mean-square measure, and the range of validity of the approach for damage detection is established. Fu...

Computational studies of a strain-based deformation shape prediction algorithm for control and monitoring applications

A modal approach is investigated for real-time deformation shape prediction of lightweight unmanned flying aerospace structures, for the purposes of Structural Health Monitoring (SHM) and condition assessment. The deformation prediction algorithm depends on the modal properties of the structure and uses high-resolution fiber-optic sensors to obtain strain data from a representative aerospace structure (e.g., flying wing) in order to predict the associated real-time deflection shape. The method is based on the use of fiber-optic sensors such as optical Fiber Bragg Gratings (FBGs) which are known for their accuracy and light weight. In this study, the modal method is examined through computational models involving Finite-Element Analysis (FEA). Furthermore, sensitivity analyses are performed to investigate the effects of several external factors such as sensor locations and noise pollution on the performance of the algorithm. This work analyzes the numerous complications and difficulties that might potentially arise from combining the state-of-the-art advancements in sensing technology, deformation shape prediction, and structural health monitoring, to achieve a robust way of monitoring ultra lightweight flying wings or next-generation commercial airplanes.

Control of a simulated wing structure with multiple segmented control surfaces

The main objective of this paper is to demonstrate that a wing with segmented control surfaces can redistribute its load, inboard or outboard, in order to perform active shape control while still maintaining level flight. Methods will be presented for controlling the plunge deflections of an aircraft wing structure. One possible solution to improving the flight envelope is a wing design with multiple segmented control surfaces all along its span. This will give an aircraft far more control over its lift distribution in comparison to a typical wing. In order to construct a wing with segmented trailing edges, it must first be shown that deflections under lift loads can be controlled. This paper introduces the research performed by the Structures, Propulsion, and Controls Engineering (SPACE) Center using a Fiber-Optic Strain-Sensing (FOSS) system that is currently implemented on the Odyssey UAV. The research will use a set of strain-based Displacement Transfer Functions (DTF) and the FOSS System both of which were developed at the NASA Dryden Flight Research Center (DFRC). Aerodynamic loads are obtained through the use of the software Athena Vortex Lattice (AVL). In addition, structural modeling is carried out with the use of finite element software. The results indicate that the shape of a wing structure can be controlled through the manipulation of segmented control surfaces to re-distribute lifting loads.

Implementation and Quantitative Analysis of a Shared-Memory Based Parallel Server Architecture for Aerospace Information Exchange Applications

This paper focuses on the implementation and quantitative analysis of a high-performance parallel processing aerospace information server. An innovative model of software architecture is provided to effectively utilize the computational power of a parallel server platform for efficient, on-demand aerospace information exchange through the Internet. This is a representative application for servers whose features are common to the classical client-server model. The server architecture supports thread, core, and/or processor-level parallel processing for high performance computing. Memory devices (i.e. cache memory, main memory, and secondary memory) are either shared or distributed among the computational units. Such features facilitate our study of identifying and overcoming the architectural bottlenecks of current commercial server configurations.

Pointing Control Testbed for Segmented Reflectors

This paper presents the research conducted at the Structures, Pointing and Control Engineering (SPACE) laboratory in achieving precision pointing of segmented reflector testbed. The systems top-level requirements include figure maintenance of the primary mirror to hold within 1 micron RMS distortion and precision pointing with accuracy of 2 are seconds. The paper focuses on the integrated analysis of the different control challenges that such advanced system would face. The objective of this research is broader in the sense that the methods and tools developed in this study shall be useful for and applicable to a broad variety of pointing control applications

Development and Implementation of an Information Server for Web-based Education in Astronomy

This paper focuses on the development of a high-performance information server for web-based education. An innovative model of software architecture is provided to effectively utilize the computational power of a parallel server platform for efficient, on-demand astronomical image browsing through the Internet. Our previous research revealed the demand for astronomical image browsing raised by various communities engaged in educational and research activities. Additionally, we have characterized network performance under different levels of activity and identified techniques for efficient image transmission over the Internet.

Implementation of a robust transmission system for astronomical images over error-prone links

The James Webb Space Telescope (JWST) is expected to produce a vast amount of images that are valuable for astronomical research and education. To support research activities related to the mission, the National Aeronautical and Space Administration (NASA) has provided funds to establish the Structures Pointing and Control Engineering (SPACE) Laboratory at the California State University, Los Angeles (CSULA). One of the research activities in SPACE lab is to design and implement an effective and efficient transmission system to disseminate JWST images across networks. In on our previous research, a prioritized transmission method was proposed to provide the best quality of the transferred image based on the joint-optimization of content-based retransmission and error concealment. In this paper, the design and implementation of a robust transmission system is presented to utilize our previously proposed methods over error-prone links. The implemented system includes three parts. First, a zero-tree based error-resilient wavelet codec is used to compress the incoming astronomical image at the sender. Tree-based interleaving is adopted in packetization to increase the systems capability to combat burst losses in error-prone channels. Second, various error concealment approaches are investigated and implemented at the receiver to improve the quality of the reconstructed image. The transmission system uses UDP as the transport protocol, but with an error control module to incorporate the optimal retransmission with the delay constraint. A user-friendly graphical interface is designed to allow easy usage for users of diverse backgrounds.

Content-based retransmission with error concealment for astronomical images

The James Webb Space Telescope (JWST) is expected to produce a vast amount of images that are valuable for astronomical research and education. To support research activities related to JWST mission, NASA has provided funds to establish the Structures Pointing and Control Engineering (SPACE) Laboratory at the California State University, Los Angeles (CSULA). One of the research activities in SPACE lab is to design an effective and efficient transmission system to disseminate JWST images across the Internet. This paper presents a prioritized transmission method to provide the best quality of the transferred image based on the joint-optimization of content-based retransmission and error concealment. First, the astronomical image is compressed using a scalable wavelet-based approach, then packetized into independently decodable packets. To facilitate the joint-optimization of two mutually dependent error control methods, a novel content index is declared to represent the significance of the packet content as well as its importance in error concealment. Based on the defined content index, the optimal retransmission schedule is determined to maximize the quality of the received image under delay constraint with the given error concealment method. Experimental results demonstrate that the proposed approach is very effective to combat the packet loss during transmission to achieve a desirable quality of the received astronomical images.

Cooperative Semi-autonomous Robotic Network for Search and Rescue Operations

The results presented in this paper prove the viability of developing a robotic network for search and rescue operations. With the capability of peer-to-peer communication, such robots form an ad-hoc network called Cooperative Mobile Network CMN. All robots in the CMN are semi-autonomous in that each operates in three modes: 1 fully controlled by a human commander; 2 controlled by a human commander for critical operations only; and 3 fully relying on its own intelligence to make decisions for cooperative operations. Due to the constraints of weight and processing power, diverse CMN operations utilize multiple robots with complementing functionalities. This work was performed at the Structures Propulsion And Control Engineering SPACE NASA sponsored University Research Center URC of excellence at the California State University, Los Angeles.

Ray tracing visualization using LabVIEW for Precision Pointing Architecture of a segmented reflector testbed

For deep space exploration, it is important for telescopes to have a high accuracy and precision in pointing at objects far in space. In addition, a large segmented space telescope requires high precision and accuracy in mirror shape. The Segmented Space Telescope Testbed at the Structures, Propulsion, and Control Engineering (SPACE) Laboratory at California State University, Los Angeles utilizes segmented mirror panels to mimic a parabolic mirror and a series of lasers and mirrors to demonstrate pointing control. This paper discusses a LabVIEW based visualization that is used for pointing simulation of the SPACE Testbed. The Visualization allows for simulation of the physical Precision Pointing Architecture (PPA) that allows for visual verification of pointing control.